Which soil classification indicates that particles fall within a narrow range regarding their size?

The classification that indicates soil particles fall within a narrow range regarding their size is uniformly graded soils. This classification signifies that the soil’s particle size distribution tends to be very similar, with little variation in size. In uniformly graded soils, there is a predominance of a narrow band of particle sizes, which can result in specific engineering properties.

Uniformly graded soils usually have a lower void ratio and may not achieve maximum density as effectively as well-graded soils, which contain a wide range of particle sizes that can effectively fill voids. In contrast, well-graded soils comprise a wide array of grain sizes, allowing more effective compaction and better engineering performance for applications like subgrade materials. Gap graded soils have specific sizes missing from the gradation, leading to a variety of voids, while coarse-grained soils focus more on the overall size category rather than the distribution pattern.

Understanding these classifications is crucial for predicting soil behavior in engineering applications and selecting appropriate soil for structural foundations, earthworks, and other civil engineering projects.